A back door, a slide door, or the like mounted on a vehicle can be opened and closed by manual manipulation. Meanwhile, there is a manipulation assisting control apparatus which applies an assisting force by a motor to make it possible to manipulate a manipulation target object with a small force in a case where the manipulation target object is opened and closed by manual manipulation.
For example, a manipulation assisting control apparatus disclosed in JP-A-2011-236697 or JP-A-2001-246936 detects an opening or closing position, a movement state, or an opening and closing manipulation force of a slide door of a vehicle by a sensor. When the sensor detects that the slide door is opened or closed on the basis of an output value of the sensor, a motor drive circuit is controlled to drive a motor and apply an assisting force for the opening and closing manipulation.
In JP-A-2001-246936, the motor drive circuit is constituted with an H-bridge circuit including four switching elements, and is connected to the motor. A relay is provided on a current path from a power supply to the motor drive circuit. When the sensor detects the opening and closing manipulation of a slide door, the relay is turned on, the current path is connected, and the current is supplied from a battery to the motor drive circuit. The motor drive circuit is controlled to cause the current to flow into the motor to drive the motor and apply an assisting force for the opening and closing manipulation of the slide door. Further, when the opening and closing manipulation of the slide door is ended or the like, the relay is turned off, the current path is disconnected, and the control of the motor drive circuit is stopped. With this, the current does not flow from the battery to the motor drive circuit or the motor, the motor is stopped, and application of the assisting force is also stopped.
However, there is a problem that when the relay is turned on or off, harsh sound is generated due to operation of an electromagnet to give a person a feeling of discomfort. As a countermeasure against the problem, for example, in an electric power steering apparatus of JP-A-2008-221862, a relay disposed between a power supply and a motor drive circuit and a motor relay disposed between the motor drive circuit and a motor are turned off in accordance with the timing of the sound occurrence accompanied by the opening and closing of a door of a vehicle after an assist control for a handle manipulation is ended. With this, the sound occurring when the relay is turned off is completely removed by the sound of opening and closing of the door and thus, it is possible to reduce the harsh sound which is given to a driver.
JP-A-2006-299603 discloses an opening and closing drive apparatus for automatically opening and closing a back door of a vehicle in accordance with switch manipulation.
In the related art, the manipulation assisting control apparatus turns a switch unit (relay or the like) provided in a current path off and interrupts flow of the current from the power supply to the motor when a manipulation target object is not manipulated in consideration of safety for preventing malfunctioning of a manipulation target object or the like and reduction of power consumption or the like.
However, if the switch unit is turned on and off each time when the manipulation of the manipulation target object is started and ended, in a case where a relay is used as the switch unit, harsh sound is generated and a feeling of discomfort is given to a manipulator. Furthermore, since the switch unit is changed from an off-state to an on-state at the time when the manipulation of the manipulation target object is started, if the motor drive circuit is controlled, driving of the motor is delayed. Since motor current flows to a motor terminal in a direction which is opposite to a desired direction by a counter electromotive force generated by rotation of a motor until the motor is driven, a manipulation load for the manipulation target object becomes heavier. When the motor is driven, an assisting force is applied for the manipulation of the manipulation target object and thus, the manipulation load for the manipulation target object becomes lighter. As described above, if the manipulation load first becomes heavier and then becomes lighter at the time when the manipulation of the manipulation target object is started, a sense of incompatibility is given to a manipulator.